Vertical axis dual vortex downwind inward flow impulse wind turbine

A method of operating a wind-powered turbine having a housing with an inlet and an outlet, a plurality of spaced-apart stators arranged in a fixed annular cylindrical stator array, a plurality of cupped rotors arranged in an annular cylindrical rotor array which is rotatable about a central axis and fits within said stator array, said stators being positioned to cause air which flows around an outer periphery of said stator array to impinge on said cupped rotors, and an air handling system which causes air entering said housing to flow around substantially the entire outer periphery of said stator array, said stator and rotor arrays being divided into a first section and a second section which are separated from one another, wherein a first portion of the air entering said housing flows through said first section and a second portion of the air entering said housing flows through said second section, including a first draft tube which directs air radially out of the center of said first section of said rotor array, and a second draft tube which directs air radially out of the center of said second section of said rotor array, said method comprising:

• (a) placing an air control valve in both of said air valves;
• and
• (b) closing the air control valve in one of said draft tubes while leaving the other of the air control valves open, to prevent air from flowing through said one of said draft tubes when the wind velocity exceeds a certain level.